In the field of medical science and research, it is often necessary to seal and unseal the open ends of centrifuge tubes, test tubes, culture tubes and the like. Medical and research technicians use centrifuges for various purposes, but mainly for separating the compounds of a multi-component fluid. The tubes used for such centrifugal separation generally include conventional glass or plastic lab tubes, or plastic tubes specifically designed to be used in centrifuge machines.
The high speed of the centrifuge process, coupled with the need to retain and control specimens in the tubes, make sealing of the open ends of the tubes with sealing caps necessary to prevent spillage or leakage. Typical closures for sealing the open end of centrifuge tubes include snap caps, such as is shown in Gerken et al. U.S. Pat. No. 4,713,219, screw caps, such as are employed for many containers; and stretchable caps, such as the stretchable cap disclosed in De Vaughn, U.S. Pat. No. 4,542,833.
When only small amounts of fluid are necessary to be centrifuged, microcentrifuge or ultracentrifuge tubes may replace normal test tubes thereby saving space and costs. Perhaps the most common microcentrifuge tubes are of the type manufactured by Bio Plas, Inc., which utilize either snap caps or screw-on caps. These snap cap tubes are available in a variety of sizes, depending on their purpose. They employ a snap cap structure including a transversely extending end wall with a cap skirt which extends into the open end of the tube. An annular protruding bead on the skirt engages and seals against the inside of the microcentrifuge tube. Screw cap tubes employ a tube body having a threaded exterior end which mates with interior threads on the cap.
Microcentrifuge tubes are used in centrifuges which operate at speeds of up to about 20,000 RPM. For some separation applications, however, even greater speeds are required. In recent years, therefore, ultracentrifuges have been developed in which angular velocities as high as 45,000 RPM are possible. Such ultracentrifuges require a tube which is closed more positively than the conventional snap caps used on microcentrifuge tubes. Moreover, as the centrifugal forces build in the ultracentrifuge range, the weight of the tube and its contents must be supported in a manner which will not force open the tube cap.
The small size and large quantity of microcentrifuge and ultracentrifuge tubes handled by lab technicians, makes snapping and unsnapping, or screwing and unscrewing the caps from the tubes quite tedious and monotonous. As the snap cap closure structure becomes more positive in its securement of the cap on the tube, the removal of the snap cap becomes quite difficult and possibly painful or injurious. The technician must grab a small protruding lip of the snap cap and pry off the cap by inserting fingertips or a prying tool between the tube and the cap. This repetitious prying technique becomes very cumbersome, and can be complicated by the need for the lab technician to wear gloves. Moreover, the process of prying snap caps off centrifuge tubes can cause contamination of the specimen in the tube.
Similarly, the screw-on cap microcentrifuge tubes require the user to properly align the screw-on caps to the tubes in order to engage the thread structure. This seemingly common task appears very simple; however, because of the small size of the objects and the shear volume in usage, the task, again, becomes quite tedious. Moreover, the screw-on caps are often misplaced between removal and remounting, rendering the tube unusable if the original cap or another cap cannot be located.
Accordingly, it is an object of the present invention to provide a centrifuge tube which is particularly suited for use in ultracentrifuges and to provide centrifuge tube and cap assembly in which the cap is more positively secured to the tube and the centrifugal forces are supported independently of the cap securement structure.
It is another object of the present invention to provide a cap manipulating tool which can be used to remove the remount snap caps and screw caps from centrifuge tubes.
It is a further object of the present invention to provide a cap manipulating tool which is suitable for use in removing and remounting of positively secured snap caps from ultracentrifuge tubes.
Another object of the present invention is to provide an apparatus and method for removing screw caps from microcentrifuge tubes and for retaining control of the caps for subsequent remounting on the tubes.
It is still another object of the present invention to provide a cap manipulating tool which reduces the risks of injury and contamination and also reduces the tedium of removing and installing caps from centrifuge tubes.
A further object of the present invention is to provide a method and device which will reduce the time required for a technician to remove and install snap caps and screw caps on microcentrifuge tubes.
Another object of the present invention is to provide a centrifuge tube and a centrifuge tube cap manipulating tool which are durable, compact, easy to maintain, are disposable, have a minimum number of components and are economical to manufacture.
Still a further object of the present invention is to provide a centrifuge tube having a snap cap with an improved sealing structure suitable for use in an ultracentrifuge.
The device of the present invention has other objects and features of advantage which will become apparent from, and are set forth in more detail in, the description of the Best Mode of Carrying Out the Invention and the accompanying drawing.